trusty (3) Type::Tiny::Manual::Params.3pm.gz

NAME

       Type::Tiny::Manual::Params - coerce and validate arguments to functions and methods

DESCRIPTION

       There is a module called Type::Params available to wrap up type coercion and constraint checks into a
       single, simple and fast check. If you care about speed, and your sub signatures are fairly simple, then
       this is the way to go...

          use feature qw( state );
          use Types::Standard qw( Str );
          use Type::Utils;
          use Type::Params qw( compile );

          my $Invocant = class_type { class => __PACKAGE__ };

          sub set_name
          {
             state $check = compile($Invocant, Str);
             my ($self, $name) = $check->(@_);

             ...;
          }

       See the COOKBOOK section of Type::Params for further information.

   The Somewhat More Manual Way...
       In general, Type::Params should be sufficient to cover most needs, and will probably run faster than
       almost anything you could cook up yourself.  However, sometimes you need to deal with unusual function
       signatures that it does not support. For example, imagine function "format_string" takes an optional
       hashref of formatting instructions, followed by a required string. You might expect to be able to handle
       it like this:

          sub format_string
          {
             state $check = compile(Optional[HashRef], Str);
             my ($instructions, $string) = $check->(@_);

             ...;
          }

       However, this won't work, as Type::Params expects required parameters to always precede optional ones. So
       there are times you need to handle parameters more manually.

       In these cases, bear in mind that for any type constraint object you have several useful checking methods
       available:

         Str->check($var)            # returns a boolean
         is_Str($var)                # ditto
         Str->($var)                 # returns $var or dies
         assert_Str($var)            # ditto

       Here's how you might handle the "format_string" function:

          sub format_string
          {
             my $instructions;
             $instructions = shift if HashRef->check($_[0]);

             my $string = Str->(shift);

             ...;
          }

       Alternatively, you could manipulate @_ before passing it to the compiled check:

          sub format_string
          {
             state $check = compile(HashRef, Str);
             my ($instructions, $str) = $check->(@_==1 ? ({}, @_) : @_);

             ...;
          }

   Signatures
       Don't you wish your subs could look like this?

          sub set_name (Object $self, Str $name)
          {
             $self->{name} = $name;
          }

       Well; here are a few solutions for sub signatures that work with Type::Tiny...

       Attribute::Contract

       You want Attribute::Contract 0.03 or above.

          use Attribute::Contract -types => [qw/Object Str/];

          sub set_name :ContractRequires(Object, Str)
          {
             my ($self, $name) = @_;
             $self->{name} = $name;
          }

       Attribute::Contract also includes support for type checking of the returned value.

       Function::Parameters

       The following should work from Function::Parameters 1.0101:

          use Function::Parameters qw(:strict);
          use Types::Standard;

          fun set_name ((Object) $self, (Str) $name)
          {
             $self->{name} = $name;
          }

          # or...
          method set_name ((Str) $name)
          {
             $self->{name} = $name;
          }

       In Function::Parameters 1.0101 and 1.0102, Moose was required to be loaded for this to work (even though
       it's not actually being used for type checks). Since Function::Parameters 1.0103, Moose is no longer
       required.

       Note the parentheses around the type names are required, because without parentheses,
       Function::Parameters will use Moose type constraints:

          method set_name (Str $name)  # Moose type constraint
          {
             $self->{name} = $name;
          }

AUTHOR

       Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

       This software is copyright (c) 2013 by Toby Inkster.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.

DISCLAIMER OF WARRANTIES

       THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
       LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.